在 dplyr 中取消引用 mutate 函数右侧的变量名 [英] Unquote the variable name on the right side of mutate function in dplyr
问题描述
我正在尝试使用 dplyr 和函数创建一个用于创建滞后变量的函数.但是,问题是我找不到如何在 mutate 函数的右侧取消引用变量名.
I am trying to make a function for a creating lagged variable using dplyr and function. But, the problem is that I cannot find how to unquote the variable name on the right side of mutate function.
mutate(dt,
!!varname_t1 := !!varname_t0 # it does not work.
)
下面是我的真实例子.
A.这是示例数据.
df <- tibble(
a = sample(5)
)
# A tibble: 5 x 1
a
<int>
1 3
2 5
3 4
4 1
5 2
我想把数据做成这样.
df <- df %>% mutate(a2 = lag(a1))
# A tibble: 5 x 2
a1 a2
<int> <int>
1 3 NA
2 1 3
3 5 1
4 2 5
5 4 2
B.我创建了一个函数,但它不起作用.我认为问题是这条线.在右侧,我不知道如何取消引用.
B. I created a function but it does not work. I think the problem is this line. On the right side, I do not know how to unquote.
!!varname_t1 := !!varname_t0
我的功能是这样的.
lag1_mutate <- function(dt, varname, time) { # time here is "after"
# enquo
varname <- enquo(varname)
time1 <- enquo(time)
time0 <- time-1; time0 <- enquo(time0)
# create the name of variables
varname_t0 <- paste0(quo_name(varname), quo_name(time0))
varname_t1 <- paste0(quo_name(varname), quo_name(time1))
# check
print(varname_t0)
print(varname_t1)
# mutate
mutate(dt,
!!varname_t1 := !!varname_t0 # <-- problem, here
# !!varname_t1 := lag(!!varname_t0) # produced only NAs
)
}
实际结果是这样的.
lag1_mutate(df, a, 2)
[1] "a1"
[1] "a2"
# A tibble: 5 x 2
a a2
<int> <chr>
1 4 a1
2 1 a1
3 3 a1
4 2 a1
5 5 a1
推荐答案
我认为您必须将 RHS 字符串转换为 quosure,您可以使用 rlang<中的
sym
/代码> 包.所以用
I think you have to convert the RHS string to a quosure, which you can do with sym
from the rlang
package. So use
mutate(dt, !!varname_t1 := lag(!!rlang::sym(varname_t0)))
那么你的函数就会产生
lag1_mutate(df, a, 1)
# [1] "a0"
# [1] "a1"
# # A tibble: 5 x 2
# a0 a1
# <int> <int>
# 1 3 NA
# 2 4 3
# 3 1 4
# 4 5 1
# 5 2 5
(你没有设置种子,所以我的tibble值和你的不同.)
(You set no seed, so my tibble values are different from yours.)
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